There is a need for a dependable mechanism for increasing the shear and flexural strengths of in-service concrete structures. This need is especially acute in ageing buildings, highways having heavy traffic, railroad bridges, and other transport related structures.
Adhesively attaching FRP sheets, laminates or strips to concrete is the most common and effective method for the strengthening of concrete structures (this is commonly referred to as externally bonded FRP, or EB-FRP). Using this method, the strength of the FRP materials is transmitted into the concrete members through adhesive bonding, however the relatively weak interface by surface adhesion between the FRPs and the concrete limits the efficacy of the method. As a result, tension failure is usually a premature, sudden and brittle detachment of the FRP from a concrete substate (unless small quantities of FRP are used).
Mechanical fastening is another technology used to bond reinforcing materials to concrete structures. Mechanical fastening relies on the bearing of the attaching material on the fasteners to transmit the interface shear, for example in steel plating the interface shear that causes the tension force in the steel plate is transmitted into the concrete substrate through the bearing of the plate holes on the bolts that are anchored into the concrete. However, mechanical fastening is not easily used with FRP materials, because FRPs do not have sufficient bearing strength. Mechanical anchors often cut through the FRP sheet and cause longitudinal splitting of FRP sheets under loading.
It is an object of the invention to provide an improved or alternative method of reinforcing concrete structures using fiber reinforced plastic.